The latest on the suburban seattle man on trial for the murder of his wife. Here than seven years after her death, his mother-in-law wouldn't give up. Now his interrogation tape is playing out in court. Here's abc's neal karlinsky. Reporter: Without a single hard piece of evidence linking david pietz to his wife's murder, prosecutors are focussing in on his character. The behavior of when his wife was found. So many pills. I don't know if I was just hoping she did or if I was thinking she flushed them down the toult. The appearance of crying. I didn't see the tears. Reporter: The long line of women he apparently cheated with. I remember kissing him. We had sex. Reporter: And there was his mother-in-law, who suspected him early on. Hounded him for the truth. And fought six long years for his arrest. If he can't take being confronted by a 72-year-old woman, well, I'm sorry. But, he's not much of a man. Reporter: Nicole pietz vani vanished in 2006. Her body was found in a wooded area, strangled. When david was arrested last year, defetectives said he wanted out of his marriage. They built a case on circumstantial evidence and dna. The cases are tough. You don't have traditionally the kind of evidence you would want. The prosecutors end up assassinating the character of the defendant. Reporter: Prosecutors tried to show that the mileage on nicole's car doesn't add up, maybe because it was used to hide her body? Is it fair to say if somebody was driving around to find a location to dump a body, they might have to drive a few more miles? Objection. Speculation. Reporter: His lawyers say the case is built on pure speculation. The prosecution continues this morning after a week off. Now to our morning exclusive

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